1. Field of the Invention
The present invention relates, generally, to a thin-film magnetic write head such as a floating type magnetic head and more particularly, the invention relates to a thin-film magnetic head in which side fringing can be appropriately suppressed and that can be fabricated with a high degree of consistency, and to a method for fabricating the same.
2. Description of the Related Art
FIG. 24 is a partial front view showing the structure of a conventional thin-film magnetic head (inductive head), and FIG. 25 is a partial sectional view of the thin-film magnetic head shown in FIG. 24. As shown in FIG. 24, insulating layers 3 are formed on both sides of a lower core layer 1 composed of a magnetic material, such as Permalloy. A gap layer 4 and an upper pole layer 5 are formed with a track width Tw on the lower core layer 1, and also are formed so as to be exposed at a surface facing a recording medium. As shown in FIG. 25, the gap layer 4 extends on the lower core layer 1 to a position at which a base 10b of an upper core layer 10, which will be described below, and the lower core layer 1 come into contact with each other, and the upper pole layer 5 extends onto a Gd-setting insulating layer 6 formed on the gap layer 4. Additionally, the gap layer 4 is composed of a nonmetallic insulating material, such as SiO2.
As shown in FIGS. 24 and 25, an insulating layer 7 is formed so as to be disposed on both sides of the upper pole layer 5 in the track width direction (in the X direction in the drawing) and to extend in the height direction (in the Y direction in the drawing). On the insulating layer 7, a coil layer 13 is spirally patterned, and the coil layer 13 is embedded in an insulating layer 9 composed of an organic insulating material.
The upper core layer 10 is formed, for example, by frame plating, on the insulating layer 9, and a tip 10a of the upper core layer 10 is magnetically coupled to the upper pole layer 5 and also is formed so as to be exposed at the surface facing the recording medium. The base 10b of the upper core layer 10 is magnetically coupled to the lower core layer 1. As shown in FIG. 24, the entirety of a tip surface 10c of the upper core layer 10 is formed so as to be exposed at the surface facing the recording medium.
A method for fabricating the thin-film magnetic head shown in FIGS. 24 and 25 will be described with reference to FIGS. 26 to 32. As shown in FIG. 26, the gap layer 4 composed of an insulating material, such as SiO2, is formed over the entire surface of the lower core layer 1, and a resist layer 11 having a groove 11a that is equal to the track width Tw is formed on the gap layer 4. The groove 11a is formed with a predetermined length from the surface facing the recording medium in the height direction (in the Y direction in the drawing). The upper pole layer 5 composed of, for example, an NiFe alloy, is plated in the groove 11a, and the resist layer 11 is removed.
As shown in FIG. 27, the width of the upper pole layer 5, i.e., the track width Tw, is set, for example, at 0.45 μm, and a height h1 is set at approximately 3.5 to 3.8 μm. Both sides of the upper pole layer 5 in the track width direction (in the X direction in the drawing) are etched by ion milling (trimming step). During the ion milling process, as shown in FIG. 28, portions of the gap layer 4 exceeding the width of the upper pole layer 5 are trimmed away and also the upper surface of the lower core layer 1 on both sides are trimmed, and thus a protrusion 1b and inclined planes 1a are formed on the lower core layer 1.
In the step shown in FIG. 29, the insulating layer 7, composed of Al2O3 or the like, is formed on the lower core layer 1 on both sides of the upper pole layer 5 so as to embed the upper pole layer 5 in the insulating layer 7. Then, as shown in FIG. 30, the insulating layer 7 is polished at the line A—A using a CMP technique.
Next, the coil layer 13 and the insulating layer 9 shown in FIG. 25 are formed. Then, as shown in partial plan view in FIG. 31, a resist layer 12 is formed over the insulating layers 7 and 9 and the upper pole layer 5. A portion corresponding to a pattern 12a of the resist layer 12 is exposed and developed, and the portion corresponding to the pattern 12a is removed.
A magnetic material is plated in the pattern 12a, and the resist layer 12 is removed, and thus the upper core layer 10 is formed. FIG. 32 shows the structure in the vicinity of the tip of the thin-film magnetic head.
The trimming step described above and shown in FIG. 27 is usually carried out twice. In the first trimming step, ion irradiation is performed substantially perpendicular to the plane direction of the lower core layer 1. In this step, the gap layer 4 extending on both sides of the lower surface of the upper pole layer 5 is trimmed, and portions of the lower core layer 1 under the gap layer 4 are also trimmed, and thus the protrusion 1b of the lower core layer 1 is formed. Since magnetic dust generated by trimming of the gap layer 4 and the lower core layer 1 adheres to the sides of the upper pole layer 5, in the second trimming step, ion irradiation is performed in more inclined directions in comparison with the first trimming step so that the magnetic dust is removed and the inclined planes 1a are formed on the lower core layer 1 on both sides of the protrusion 1b. 
However, in the thin-film magnetic head shown in FIGS. 24 and 25, since the tip surface 10c of the upper core layer 10 having a width larger than the track width Tw is formed so as to be exposed at the surface facing the magnetic medium, side fringing occurs between the upper core layer 10 and the upper pole layer 5 due to magnetic leakage, resulting in a decrease in a real density.
Consequently, in order to fabricate a thin-film magnetic head which is suitable for an increased recording density, in addition to a decrease in the track width Tw, side fringing must be reduced.
In the method for fabricating the thin-film magnetic head shown in FIGS. 24 and 25, the trimming step is carried out, and in the trimming step, variations in the track width Tw and in the shape occur, and also the height of the upper pole layer 5 is significantly decreased.
The reason for carrying out the trimming step is that in the state shown in FIG. 27, since the gap layer 4 and the lower core layer 1 extend on both sides of the lower surface of the upper pole layer 5, side fringing easily occurs between the upper pole layer 5 and the lower core layer 1. As shown in FIG. 28, by trimming the gap layer 4 extending on both sides of the lower surface of the upper pole layer 5 and by further forming the protrusion 1b and the inclined planes 1a, the distance between the upper pole layer 5 and the lower core layer 1 can be increased, and thus the side fringing is believed to be appropriately suppressed.
However, when the trimming step is carried out, variations in the amount of magnetic dust adhering to both sides of the upper pole layer 5 and variations during the removal of the magnetic dust occur. Also, as described above, in the first trimming step, since the ion irradiation is performed substantially perpendicular to the plane direction of the lower core layer 1, the height of the upper pole layer 5 is significantly decreased. As a result, variations easily occur in the track width Tw and the shape of the upper pole layer 5, and a significant decrease in the height of the upper pole layer 5 and variations in the height may also occur.
Consequently, if the trimming step is carried out, the uniformity during the fabrication of thin-film magnetic heads is reduced, and due to the decrease in the height of the upper pole layer 5, the volume of the upper pole layer 5 is decreased. Thus, the upper pole layer 5 is easily magnetically saturated, resulting in degradation in recording characteristics.